Filler panels are conventionally used in conjunction with various computer chassis for electromagnetic interference (EMI) containment as well as for sealing of the computer chassis/card cage for thermal (e.g. forced airflow) cooling purposes. Specifically, in a conventional computer chassis/card cage assembly, multiple slots are available to receive a corresponding printed circuit assembly (PCA). The filler panels are attached to the computer chassis to enclose or seal off regions/slots of the computer chassis which do not have a printed circuit assembly (PCA) disposed therein. Typically, conventional filler panels are attached to the computer chassis using captive screws. The captive screws are disposed on the filler panels at locations corresponding to mounting holes residing within the computer chassis.
The location and the spacing of mounting holes within the computer chassis (and the corresponding location of the captive screws on the filler panels) are often defined by an industry standard. Typical standards include, for example, the compact peripheral component interconnect (CPCI) standard, and the VersaModular Eurocard (VME) standard. For example, the CPCI standard dictates that the gap between adjacent units (e.g. adjacent filler panels, adjacent PCAs, or a PCA and an adjacent filler panel) be nominally set at 0.30 millimeters. Unfortunately, industry standard captive screws allow the filler panel to be mispositioned by more than 1.0 millimeter. For purposes of the present application, this mispositioning with respect to the computer chassis, caused in some cases by the use of captive screws, is referred to as interference generating movement. During use, the interference generating movement of the filler panels can deleteriously prevent insertion of a PCA or a filler panel. That is, interference generating movement of one or more filler panels can result in insufficient space in a neighboring slot such that a filler panel or a PCA will not fit in the compromised gap.
With reference now to Prior Art FIG. 1, an example of a compromised gap produced as a result of interference generating movement of a filler panel is clearly illustrated. As shown in Prior Art FIG. 1, a portion of a computer chassis 100 is depicted having mounting holes, typically shown as 102, therein. A filler panel 104 is shown coupled to computer chassis 100 and, for purposes of illustration, filler panel 104 is depicted as being coupled to computer chassis 100 without any substantial interference generating movement. Another filler panel 106 is also shown coupled to computer chassis 100. In this example, filler panel 106 is depicted as being coupled to computer chassis 100 with substantial interference generating movement due to the use of captive screws 107a and 107b. Specifically, filler panel 106 is depicted as having been mispositioned in a direction towards neighboring gap 108 and filler panel 104. Dotted line 110 illustrates the desired or nominal location of filler panel 106 assuming no interference generating movement. Because of the interference generating movement of filler panel 106, the width, w, of gap 108 is less than the width of a filler panel or a PCA. Hence, it is no longer possible to readily place a filler panel or a PCA into gap 108. Additionally, the width of gap 108 may be even further compromised (i.e. reduced) in the case where filler panel 104 suffers from interference generating movement which mispositions filler panel 104 in a direction towards neighboring gap 108 and filler panel 106.
At present, one approach to fix the problem described above, is to first have all of the necessary filler panels loosely connected to the computer chassis. Once all of the filler panels are in place, the filler panels are then carefully tightened to the computer chassis in order to insure that interference generating movement is reduced as much as possible. However, such a method is time-consuming, cumbersome, and lacks the desired “Design for Manufacturability (DFM).”
The problem described in conjunction with Prior Art FIG. 1 is particularly egregious in light of the increased prevalence of “hot swapping.” Hot swapping refers to a process in which a PCA is added to or removed from the computer chassis without powering down the system. With hot swapping, it is imperative that interference generating movement is reduced in order to facilitate rapid and perhaps frequent removal and addition of PCAs and filler panels.
One prior art attempt to resolve the problem of interference generating movement involves customizing a computer chassis with a non-standard sheet metal interface having predefined openings formed therein. Specially designed filler panels are also employed in conjunction with the non-standard customized computer chassis. Such an approach has severe drawbacks associated therewith. For example, a non-standard customized chassis allows DFM tolerancing that makes is very difficult to hold CPCI standard specifications. Furthermore, limiting customers to the use of one particular design/maker of filler panels is not favorable.
A further drawback of prior art filler panels is the mounting method for captive screws used in conjunction with filler panel assemblies. Specifically, as stated above, a filler panel mounted to a chassis is a tight fit. In fact, if captive screws are not utilized, ensuring a proper fit between the chassis and the filler panel is extremely difficult. In addition, since a filler panel is required for each slot not occupied with any type of complete assembly (i.e. any empty slot), on any given chassis, the number of empty slots can be extensive. As such, the multiplicity of required filler panels translates into a multiplicity of captive screw mounts. For example, FIG. 3 illustrates a keyed filler panel assembly 300 in which the attaching device is comprised of a captive screw 204 and an underlying D-clip 302.
It is appreciated that each underlying D-clip 302 has an associated per item cost. It is further appreciated that a second cost is accrued with regard to assembly. Specifically, for every part required in the assembly operation, time and labor factors must be accounted for in the assembly process. That is, time and labor requirements translate into accrued costs. As a result, the associated costs of a filler panel assembly can deleteriously effect company profit.
A further problem has arisen with regard to the removal of filler panel assemblies. Specifically, as stated above, a filler panel mounted to a chassis is a tight fit. In fact, the EMI gasket causes a friction force which helps hold a filler panel in-place. Further, as shown in Prior Art FIG. 1, the face of the filler panel is smooth with nothing to grasp. Thus, with a multiplicity of filler panels or complete assemblies mounted on a chassis, removal of a single filler panel is both difficult and time consuming.